Direct fire weapons are weapons that require a line-of-sight between the weapon and the target. Examples of direct fire weapons include rifles, machine guns, canon, short range missiles and directed energy weapons. Examples of indirect fire weapons include artillery, mortars, and long-range missiles.
Until the middle of the 20th century, direct fire weapons were fired manually by a gunner positioned directly behind the weapon. The advantages of remote operation (e.g. of machine guns during trench warfare) were observed in the early 20th century, but the technology did not exist to allow remote operation without substantially degrading overall combat effectiveness.
By 1980 it was widespread practice to include as secondary armament on a main battle tank, small arms with either remote control or armour cover, or both. Small arms, generally defined as ballistic weapons with a calibre of less than 40 mm, are direct fire weapons.
By 1990 the increased emphasis on maximizing both mobility and firepower resulted in various proposals for remotely operated weapon stations, in which small arms are mounted on motorized brackets and remotely operated. Typically these systems comprise a machine gun roof-mounted on a lightly armored or unarmored vehicle, and operated under manual control from within the vehicle.
These systems offer several advantages, including:                the use of a remote gunner lowers the center of mass of the weapon system, allowing heavier weapons to be mounted on lighter vehicles without compromising stability;        the relocation of the gunner obviates the need for a turret, allowing weight savings that lead to increased mobility;        protection of the gunner improves weapon aiming and combat effectiveness;        the relocation of the gunner hardens the weapon system as a target, making it more difficult to disable than a manned weapon; and        vehicle hull penetration by the weapon system can be reduced to small mounting holes, thus increasing the survivability of the vehicle. The large hole required for a human operator is not required.        
More recently, gyro-stabilized remotely-controlled weapon systems have been proposed (Smith et al, U.S. Pat. No. 5,949,015 dated Sep. 7, 1999). These gyro-stabilized remote weapon control systems have the additional advantage that the aiming point of the weapon may be rendered substantially independent of motion of the weapon platform.
Notwithstanding the advantages of remote weapon systems, their shortcomings include:                Poor accuracy. The use of manual weapon pointing, even if stabilized for weapon platform motion, does not allow optimum use of weapons. The most common and inexpensive direct-fire weapons have inherent accuracy that exceeds the ability of human gunners to aim the weapon.        Poor ergonomics. Typical implementations of remote weapon systems require int nse multi-tasking of the remot gunner under combat stress, particularly if the weapon is vehicle-mounted. This reduces the effectiveness of the weapon system.        Poor stabilization. Gyro-stablized weapon systems seek to maintain weapon aiming accuracy by compensating for the motion of the weapon platform. For each axis of potential motion of the weapon, gyro is required, as well as a corresponding servo-controlled axis on the weapon mount. This results in costly systems that do not take into account movement of the target, and are of limited use in realistic combat situations involving target motion.        